/******************************************************************
 *
 * Copyright 2018 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 ******************************************************************/

/****************************************************************************
 *
 *   Copyright (C) 2016-2018 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <stdint.h>
#include <sched.h>
#include <debug.h>

#include <tinyara/irq.h>
#include <tinyara/arch.h>

#include "sched/sched.h"
#include "xtensa.h"

#include "irq/irq.h"

#ifndef CONFIG_DISABLE_SIGNALS

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_schedule_sigaction
 *
 * Description:
 *   This function is called by the OS when one or more
 *   signal handling actions have been queued for execution.
 *   The architecture specific code must configure things so
 *   that the 'sigdeliver' callback is executed on the thread
 *   specified by 'tcb' as soon as possible.
 *
 *   This function may be called from interrupt handling logic.
 *
 *   This operation should not cause the task to be unblocked
 *   nor should it cause any immediate execution of sigdeliver.
 *   Typically, a few cases need to be considered:
 *
 *   (1) This function may be called from an interrupt handler
 *       During interrupt processing, all xcptcontext structures
 *       should be valid for all tasks.  That structure should
 *       be modified to invoke sigdeliver() either on return
 *       from (this) interrupt or on some subsequent context
 *       switch to the recipient task.
 *   (2) If not in an interrupt handler and the tcb is NOT
 *       the currently executing task, then again just modify
 *       the saved xcptcontext structure for the recipient
 *       task so it will invoke sigdeliver when that task is
 *       later resumed.
 *   (3) If not in an interrupt handler and the tcb IS the
 *       currently executing task -- just call the signal
 *       handler now.
 *
 ****************************************************************************/

#ifndef CONFIG_SMP
void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
{
	irqstate_t flags;

	svdbg("tcb=0x%p sigdeliver=0x%p\n", tcb, sigdeliver);

	/* Make sure that interrupts are disabled */

	flags = up_irq_save();

	/* Refuse to handle nested signal actions */

	if (!tcb->xcp.sigdeliver) {
		/* First, handle some special cases when the signal is being delivered
		 * to the currently executing task.
		 */

		svdbg("rtcb=0x%p CURRENT_REGS=0x%p\n", this_task(), CURRENT_REGS);

		if (tcb == this_task()) {
			/* CASE 1:  We are not in an interrupt handler and a task is
			 * signaling itself for some reason.
			 */

			if (!CURRENT_REGS) {
				/* In this case just deliver the signal now.
				 * REVISIT:  Signal handler will run in a critical section!
				 */

				sigdeliver(tcb);
			}

			/* CASE 2:  We are in an interrupt handler AND the interrupted
			 * task is the same as the one that must receive the signal, then
			 * we will have to modify the return state as well as the state
			 * in the TCB.
			 *
			 * Hmmm... there looks like a latent bug here: The following logic
			 * would fail in the strange case where we are in an interrupt
			 * handler, the thread is signaling itself, but a context switch
			 * to another task has occurred so that CURRENT_REGS does not
			 * refer to the thread of this_task()!
			 */

			else {
				/* Save the return pc and ps.  These will be restored by the
				 * signal trampoline after the signals have been delivered.
				 *
				 * NOTE: that hi-priority interrupts are not disabled.
				 */

				tcb->xcp.sigdeliver = sigdeliver;
				tcb->xcp.saved_pc = CURRENT_REGS[REG_PC];
				tcb->xcp.saved_ps = CURRENT_REGS[REG_PS];

				/* Then set up to vector to the trampoline with interrupts
				 * disabled
				 */

				CURRENT_REGS[REG_PC] = (uint32_t)_xtensa_sig_trampoline;
#ifdef __XTENSA_CALL0_ABI__
				CURRENT_REGS[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM);
#else
				CURRENT_REGS[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM | PS_WOE);
#endif

				/* And make sure that the saved context in the TCB is the same
				 * as the interrupt return context.
				 */

				xtensa_savestate(tcb->xcp.regs);
			}
		}

		/* Otherwise, we are (1) signaling a task is not running from an
		 * interrupt handler or (2) we are not in an interrupt handler and the
		 * running task is signaling some non-running task.
		 */

		else {
			/* Save the return pc and ps.  These will be restored by the
			 * signal trampoline after the signals have been delivered.
			 *
			 * NOTE: that hi-priority interrupts are not disabled.
			 */

			tcb->xcp.sigdeliver = sigdeliver;
			tcb->xcp.saved_pc = tcb->xcp.regs[REG_PC];
			tcb->xcp.saved_ps = tcb->xcp.regs[REG_PS];
			/* Then set up to vector to the trampoline with interrupts
			 * disabled
			 */

			tcb->xcp.regs[REG_PC] = (uint32_t)_xtensa_sig_trampoline;
#ifdef __XTENSA_CALL0_ABI__
			tcb->xcp.regs[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM);
#else
			tcb->xcp.regs[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM | PS_WOE);
#endif
		}
	}

	up_irq_restore(flags);
}
#endif							/* !CONFIG_SMP */

#ifdef CONFIG_SMP
void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
{
	irqstate_t flags;
	int cpu;
	int me;

	svdbg("tcb=0x%p sigdeliver=0x%p\n", tcb, sigdeliver);

	/* Make sure that interrupts are disabled */

	flags = up_irq_save();

	/* Refuse to handle nested signal actions */

	if (!tcb->xcp.sigdeliver) {
		/* First, handle some special cases when the signal is being delivered
		 * to task that is currently executing on any CPU.
		 */

		svdbg("rtcb=0x%p CURRENT_REGS=0x%p\n", this_task(), CURRENT_REGS);

		if (tcb->task_state == TSTATE_TASK_RUNNING) {
			me = this_cpu();
			cpu = tcb->cpu;

			/* CASE 1:  We are not in an interrupt handler and a task is
			 * signaling itself for some reason.
			 */

			if (cpu == me && !CURRENT_REGS) {
				/* In this case just deliver the signal now.
				 * REVISIT:  Signal handler will run in a critical section!
				 */

				sigdeliver(tcb);
			}

			/* CASE 2:  The task that needs to receive the signal is running.
			 * This could happen if the task is running on another CPU OR if
			 * we are in an interrupt handler and the task is running on this
			 * CPU.  In the former case, we will have to PAUSE the other CPU
			 * first.  But in either case, we will have to modify the return
			 * state as well as the state in the TCB.
			 */

			else {
				/* If we signaling a task running on the other CPU, we have
				 * to PAUSE the other CPU.
				 */

				if (cpu != me) {
					/* Pause the CPU */

					up_cpu_pause(cpu);

					/* Wait while the pause request is pending */

					while (up_cpu_pausereq(cpu)) {
					}

					/* Now tcb on the other CPU can be accessed safely */

					/* Copy tcb->xcp.regs to tcp.xcp.saved. These will be restored
					 * by the signal trampoline after the signal has been delivered.
					 *
					 * NOTE: that hi-priority interrupts are not disabled.
					 */

					tcb->xcp.sigdeliver = sigdeliver;
					tcb->xcp.saved_pc = tcb->xcp.regs[REG_PC];
					tcb->xcp.saved_ps = tcb->xcp.regs[REG_PS];

					/* Then set up to vector to the trampoline with interrupts
					 * disabled
					 */

					CURRENT_REGS[REG_PC] = (uint32_t)_xtensa_sig_trampoline;
#ifdef __XTENSA_CALL0_ABI__
					CURRENT_REGS[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM);
#else
					CURRENT_REGS[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM | PS_WOE);
#endif
				} else {
					/* tcb is running on the same CPU */

					/* Copy tcb->xcp.regs to tcp.xcp.saved. These will be restored
					 * by the signal trampoline after the signal has been delivered.
					 *
					 * NOTE: that hi-priority interrupts are not disabled.
					 */

					tcb->xcp.sigdeliver = sigdeliver;
					tcb->xcp.saved_pc = CURRENT_REGS[REG_PC];
					tcb->xcp.saved_ps = CURRENT_REGS[REG_PS];

					/* Then set up to vector to the trampoline with interrupts
					 * disabled
					 */

					CURRENT_REGS[REG_PC] = (uint32_t)_xtensa_sig_trampoline;
#ifdef __XTENSA_CALL0_ABI__
					CURRENT_REGS[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM);
#else
					CURRENT_REGS[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM | PS_WOE);
#endif
					/* And make sure that the saved context in the TCB is the same
					 * as the interrupt return context.
					 */

					xtensa_savestate(tcb->xcp.regs);
				}

				/* Increment the IRQ lock count so that when the task is restarted,
				 * it will hold the IRQ spinlock.
				 */

				DEBUGASSERT(tcb->irqcount < INT16_MAX);
				tcb->irqcount++;

				/* In an SMP configuration, the interrupt disable logic also
				 * involves spinlocks that are configured per the TCB irqcount
				 * field.  This is logically equivalent to up_irq_save().
				 * The matching call to up_irq_restore() will be
				 * performed in up_sigdeliver().
				 */

				//spin_setbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,&g_cpu_irqlock);

				/* RESUME the other CPU if it was PAUSED */

				if (cpu != me) {
					up_cpu_resume(cpu);
				}
			}
		}

		/* Otherwise, we are (1) signaling a task is not running from an
		 * interrupt handler or (2) we are not in an interrupt handler and the
		 * running task is signaling some other non-running task.
		 */

		else {
			/* Save the return pc and ps.  These will be restored by the
			 * signal trampoline after the signals have been delivered.
			 *
			 * NOTE: that hi-priority interrupts are not disabled.
			 */

			tcb->xcp.sigdeliver = sigdeliver;
			tcb->xcp.saved_pc = CURRENT_REGS[REG_PC];
			tcb->xcp.saved_ps = CURRENT_REGS[REG_PS];

			/* Increment the IRQ lock count so that when the task is restarted,
			 * it will hold the IRQ spinlock.
			 */

			DEBUGASSERT(tcb->irqcount < INT16_MAX);
			tcb->irqcount++;

			/* Then set up to vector to the trampoline with interrupts
			 * disabled
			 */

			tcb->xcp.regs[REG_PC] = (uint32_t)_xtensa_sig_trampoline;
#ifdef __XTENSA_CALL0_ABI__
			tcb->xcp.regs[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM);
#else
			tcb->xcp.regs[REG_PS] = (uint32_t)(PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM | PS_WOE);
#endif
		}
	}

	up_irq_restore(flags);
}
#endif							/* CONFIG_SMP */

#endif							/* !CONFIG_DISABLE_SIGNALS */
